This paper briefly discusses the relevance of small-scale biomass combustion systems for European renewable energy policy. Moreover, the state-of-the-art of modern small-scale biomass combustion systems is presented. The different technologies are reviewed regarding emissions and efficiency for different biomass. On-going developments and innovative approaches are presented and discussed.

Straw, Miscanthus, maize, and horse manure were reviewed in terms of fuel characteristics. They were tested in existing boilers, and the particulate and gaseous emissions were monitored. The ash was analyzed for the presence of sintered material. All the fuels showed problems with ash lumping and slag formation. Different boiler technologies showed different operational performances. Maize and horse manure are problematic fuels regarding NO_x and particulate emissions. Miscanthus was the best fuel tested. Due to the big variation of fuel properties and therefore combustion behavior of agricultural biomass, further R&D is required to adapt the existing boilers for these fuels.

Experimental data on the release of NO_x precursors from solid biomass fuels during thermal conversion are necessary to study N release in general and to supply reliable data for the purpose of packed bed and gas phase conversion model development and validation. In this work the release of NO_x precursors was studied at a lab-scale pot furnace (batch reactor) by taking measurements during the conversion process of solid biomass in a packed bed. The investigations were carried out with relevant woody biomass fuels, which cover a broad range of fuel N contents: sawdust, bark, waste wood and MDF board. The most important NO_x precursor detected above the fuel bed under fuel rich conditions was NH₃, while HCN was almost insignificant with the exception of sawdust. NO was detected mainly under air rich conditions. Furthermore, the experimental data were utilised to derive release functions for the relevant NO_x precursors NO, NH₃ and HCN. The release functions were implemented in an in-house empirical packed bed combustion model, which serves as a basis for a subsequent CFD N species gas phase calculation. © 2007 Elsevier Ltd. All rights reserved.

For an appropriate operation of a heat exchanger it is very helpful to know its dynamic behaviour. To this a simple sufficient accurate nonlinear model for the description of the dynamic behaviour is derived on the basis of a gas tube heat exchanger. Due to the general approach used for the derivation the model could be adaptet easily for other types of heat exchangers. The presented model can be used to estimate not measured physical values, to monitor the deposit formation in the heat exchanger and as a basis for the design of a model based control strategy. © Oldenbourg Wissenschaftsverlag.

The availability of energy is important to our every day lives. Biomass-fuelled heating systems are comfortable and reach an efficiency form over 90 %. With a thermoelectric generator (TEG) it’s possible to convert a part of the heat directly into electrical power and so become self sufficient from electicity. The purpose of this thesis was to optimise an existing prototype of a combined heat and power (CHP) plant based on a pellet heating system and a thermoelectric generator. Balancing the energy flows, especially the losses, was also part of the thesis.
Tests with the prototype were done. Some with the originial prototype, some with additional insulation and some with preheating the combustion air. To examine the part load behaviour, tests were done at 10, 7 and 4 kW fuelheat input.
By insulating the TEG the performance rose from 153 W to 174 W. The insulation and the preheating of the combustion air from room temperature to 350 degree lead to an power output from 194 watt. All at 10 kW fuellheat input. Finally the following conclusions can be drawn: For the series product it is recommended to optimize the insulation of the TEG. As the preheating of the combustion air didn’t lead to the expected effects it should be left out.

This paper presents one part of the results of a project dealing with straw pellets combustion in small
scale combustion systems. Whereas the other part of the work investigates gaseous and particulate emissions, this part focuses on the results of experiments to determine corrosion of refractory material. Three different types of straw
pellets are combusted in a prototype of a 15 kW residential heating boiler. The fuel samples are natural wheat straw,
wheat straw with alumina based additive and wheat straw with a mixture of calcium-/magnesium carbonate based
additive. Combustion experiments are performed under different operating conditions of the test boiler. Three
different types of refractory material are used as combustion chamber material. The refractory materials are different
mixtures of alumina, silica, zirconia and silicium-carbide. The degree of deterioration of these materials is
investigated for temperatures between 700 and 1300 deg C in the presence of slag formed during combustion of the
straw samples and the influence of the fuel additives on corrosion effects is analysed.

The primary energy consumption world-wide is rising constantly. Therefore it is necessary to open up renewable resources for energy production. Besides wood, the application of agricultural resources and residuals for energy production is possible, also within the range of small scale combustion units. These fuels still pose a challenge, concerning gaseous and particulate emissions. This work examines the application of straw pellets in a small scale combustion unit. Gaseous and particulate emissions, as well as the separation eciency of a secondary heat exchanger with scrubber were investigated. Compared with wood-like fuels a strong slagging of the combustion chamber could be determined. Gaseous emissions as NO_x, SO₂ and HCl, as well as the emission of particles were clearly higher than with combustions of wood. The gaseous emissions were below the considered limit value for other biogenous fuels after Art. 15 a B-VG 2007 [1]. The burnout of the gaseous phase, which can be evaluated by the emission of CO, was always good and comparable with the combustion of wood.
Using a secondary heat exchanger with scrubber (Hydrocube R of the company Schräder ) particulate emissions could be reduced by 20%. Element analysis of the particulate emissions as well as particle size measurements showed that primarily large particles were separated. A retrot of the Hydrocube R by an ionizing electrode increased the degree of separation on 60%. Besides the separation of particles, the Hydrocube R also reduced gaseous emissions like SO₂ and HCl. The absorption of these components in the condensate phase caused a decrease of the pH value. Low ph value increased the corrosion of the Hydrocube R , what could be detected by rising concentrations on Fe, Ni and Cr in the condensate.

A cell agglomeration algorithm is proposed to mitigate the computational cost of incorporating detailed chemical kinetics in multi-dimensional Computational Fluid Dynamics (CFD) simulations. Cells that are close in species and energy composition space are agglomerated before calling the reaction integrator, substantially reducing the number of chemistry integrations. The algorithm is generalized and applicable to any reacting flow configuration, and the accuracy is fully controllable. A dynamic hash table is used to efficiently bin cells into high dimensional hyper-cubes in composition space. The method is applied to four different CFD simulations and the speed-up and incurred error are assessed for a range of agglomeration tolerances and table dimensions. The proposed approach exhibits up to an order of magnitude speed-up with a relatively moderate decrease in accuracy.

The project BioHeatLABEL aims at the derivation of eco-design criteria for small scale biomass
combustion systems. It is a mirror project to the on-going European preparatory study for solid fuel small combustion installations. The presented paper gives an overview of the on-going work. It presents the applied methodologies so far. Sales and performance data as well as prices are collected for the existing stock as well as for new products. Six Base Cases are defined to best possibly represent market relevant product categories. These Base Cases are (1) log wood boilers with natural draught, (2) log wood boilers with forced draught, (3) wood chips boilers, (4) wood pellets boilers, (5) log wood stoves, and (6) wood pellets stoves. For these product categories the bills of production materials as well as for packaging are collected and information about the end-of-life behaviour is retrieved. Based on the above, preliminary life cycle assessment calculations are performed using the tool EuP EcoReport. The usability of this tool for a sound, reliable and representative life cycle assessment is discussed. Finally, an outlook on the further work is given.

Driven by increasing energy and raw material prices as well as changes in the legal framework the state of the art in the European Union has changed from waste management to resource management over the past 15 years. This has led to a higher appreciation of the resource “waste” as a secondary raw material as well as an energy resource. In this context the importance of effective waste processing in order to allow quality specific routing of waste streams has become very important. On the one hand material recycling requires a high purity of the waste material to be recycled. The prices to be achieved for the recycling material are highly dependend on the purity of the recyclables. The economic viability of treatment concepts very much depends on the rate of recovery of the recycling product. On the other hand the portion of waste that is thermally treated has increased and still is on the rise. Furthermore extensive efforts on the usage of waste fractions as Solid Recovered Fuels (SRF) in alternative thermal treatment processes with higher energy recovery are being undertaken. Alternative thermal treatment
processes have special demands on the quality of the waste streams to be treated due to process and product quality reasons as well as ecological concerns. Sophisticated waste pre-treatment concepts ensure compliance with required quality standards of wastes to be recycled or utilized energetically. In spite of that waste pre-treatment - in sometimes complex processes - the problem of disposal of the remaining residual waste fraction has to be solved, as the disposal of the residuals in compliance with the regulatory framework causes high expenses for the waste treatment plant operator. The first part of this manuscript focusses on the legal framework prompting the implementation of new waste processing technologies allowing an effective routing of waste fractions by material specific splitting of the over all waste stream. Most relevant in that respect are the EU Waste Framework Directive as well as the EU Landfill Directive and the EU Packaging Directive. Climate
policy and respective regulations are also influencing waste management practice. Additionally economic aspects for destination-process specific routing of waste streams are being addressed. In the second part of this manuscript the set-up of test runs as well as the results obtained and experiences gained based on the test runs are being reported. One test set-up aims at removing highcaloric waste components from waste streams of Mechanical-Biological Treatment (MBT) facilities in order to maximize the quantity of waste that can be landfilled. A second test set up deals with the processing of commercial plastic waste containing different types of polymers in order to gain pure recyclables. As the economic value of waste plastic depends on the purity in terms of individual polymers it is very important to separate individual polymers from mixed plastic waste. Near-Infrared
(NIR) sensor based sorting allows a separation of different types of plastics. The results of test runs are explained in terms of quality and yield of product gained as well as economical aspects. Although the prices for recyclables have fallen during the last months as a result of the financial and economical crisis leading to a decrease in the demand of recyclables it is assumed that gaining high quality waste fractions from mixed wastes for material recyling as well as energy recovery will become more important in the long run.

The global warming, the increasing CO2 emission, the combustion and dependency on fossil fuels, as well as the high-energy prices have resulted in an increasing demand in renewable energy sources. Biomass, as a renewable energy source, has the potential to contribute to the future energy mix in many countries. In this thesis the so-called low temperature or slow pyrolysis is chosen to convert biomass into energy rich products. Pyrolysis is a process to convert biomass directly into solid, liquid and gaseous products by thermal decomposition in absence of oxygen. The goal of the pilot plant Dürnrohr is to generate a combustible gas to substitute fossil fuels in the thermal power plant Dürnrohr. The complete process consists of individual steps. First of all the biomass is pyrolysed and pyrolysis gas and pyrolysis char are produced. The obtained pyrolysis gas is combusted in a fluidized bed combustion chamber implemented as afterburner. The following step is fluidized bed combustion of
the intermediate-stored pyrolysis char. Due to the use of different biomasses and adjustment of the individual steps, the process should be optimized for the application for the power plant Dürnrohr. One major point of the production of the pyrolysis gas is the amount of tar. The tar amount was analyzed during pyrolysis operation to find out how much tar is produced at which process settings with a main focus on the temperature. The gravimetric
analysis included gravimetric tar, dust, entrained char, water content and ph-value, as well as the GC/MS tars of the pyrolysis gas. All these data was sampled, analyzed and evaluated as well as discussed.

Wood pellet combustion units are a comfortable, full automatic and low emission solution for the provision of space heating in small scale applications. The requirement of an auxiliary energy source for the heat supply and distribution however results in a dependence on the electrical grid. The goal of this work is thereby to eliminate this dependence and to meet the auxiliary energy demand through the independent production of electrical energy. The thermoelectric power production method was chosen from a number of technology variations so as to guarantee the silent and maintenance free production of direct current that can be implemented in cellars and space heaters. The first development step was the implementation of a Prototype with a fuel heat input of 10 kW and a nominal electrical power of 200 W. The central point of the implementation was the integration of a thermo-generator in a pellet combustion unit and the subsequent evaluation of the system concept. The integrated system implemented in the prototype confirms the feasibility of the combination of these technologies. The electrical efficiency of the thermo-generator was found to be in accordance with the target value of 4%, corresponding to a produced nominal electric power of 200 W.

Holzpellets werden in zunehmendem Maße aus Hackschnitzel hergestellt. Es ist davon auszugehen, dass diese Veränderung der Rohstoffbasis zu erhöhten Aschegehalten im Brennstoff führt und zu Schwierigkeiten bei der Nutzung führen kann. Die vorliegende Arbeit kommt zum Schluss, dass moderate Anteile (< 5%) sauberer Rinde zu keinen wesentlichen Verschlackungen führen. Bei Verunreinigung oder / und sehr hohen Rindenanteilen ist mit
Verschlackungsproblemen jedenfalls zu rechnen.

In the presented work the fuel quality and basic data about production processes of wood pellets from
all over Europe are investigated. For this purpose pellets producers were interviewed and fuel samples were analysed. Information from 91 companies was evaluated, covering about 50% of the European pellets production capacity, and pellets samples of 51 companies from 18 different countries were examined. It was found, that the raw material for pellets production is mainly taken from local resources. 75% of the plants process soft wood, whereas the use of hard wood is more common in Eastern Europe, Italy, Spain and France. Regarding the fuel properties of the pellets, differences were mainly found with regard to ash content and mechanical durability. In spite of these strong variations, almost all samples fulfilled the requirements according to the respective quality standard declared, and a clear correlation of valid standards and available pellets qualities was observed.

Thermal treatment of residues and waste is an important issue with increasing demand. In this work two pathways of thermal waste treatment, incineration and gasification, are compared. For this purpose literature on both technologies has been reviewed and the state-of-art technology for waste incineration and gasification is presented. The comparison highlights the strengths and weaknesses of both technologies and identifies future potentials.

More and more waste is generated every year, which has to be disposed. There is a legal obligation to treat waste before it can be landfilled in the European Union. Thus, thermal waste treatment is a very important issue.
In this work two pathways of thermal waste treatment, incineration and gasification, are compared. For this purpose, literature on both technologies has been reviewed and the stateof‐art technology for waste incineration and gasification is presented. The comparison highlights the strengths and weaknesses of both technologies and identifies future potentials. In Europe waste incineration is the state‐of‐the‐art technology ensuring destruction of the pollutants and allowing recovery of the energy content of the waste. A waste incineration plant consists of a furnace, where the waste is incinerated and the chemically bonded energy of the waste is discharged as heat. The hot flue gases pass the heat to the water in the heating surfaces of the steam generator. The energy of the waste can be used for the generation of hot water, steam of electrical power. Then the flue gas has to be cleaned in the air pollution control system. Dust is precipitated, HCl and HF is removed in an acid scrubber and SO2 in an alkaline scrubber. A catalytic reaction destroys dioxins and furans and reduces the emissions of NOx. Due to waste incineration the volume of the residues, which have to be landfilled, is
reduced by 90%. The second pathway of thermal waste treatment is waste gasification, where solid carbonaceous materials are converted into combustible gases by reaction with gasification agents. Due to gas production, not only the energy content of the waste can be recovered but the product range is extended. The producer gas can be converted into heat and power in a conventional steam boiler but also combusted in gas engines or turbines with higher efficiencies. In a combined cycle plant the hot exhaust gas of the turbine can be used in a heat recovery steam generator to increase the efficiency even more. After further cleaning the producer gas is also a suitable feedstock for synthesis of liquid fuels, synthetic natural gas and other chemicals.
Waste gasification processes have been developed in the past, but the plants have been shut down because of economic reasons and/or technical problems. However, important research has been done in the field of biomass gasification and thus gasification technology has been improved markedly. The fluidised bed gasifier in Güssing is one of the most successful examples; this technology is about to be commercialised. Considering these developments, there is definitely interesting potential for waste gasification now and the design of a new waste gasification process based on the findings in biomass gasification will be the scope of future research work.

The global warming, the increasing CO2 emission, the combustion of and dependency on fossil
fuels, as well as the high-energy price have resulted in an increasing demand in renewable energy
sources. Biomass, as a renewable energy source, has the potential to contribute to the future energy
mix in various ways. In thermo-chemical biomass conversion processes, especially gasification and pyrolysis, the tar content and its composition is a major subject. Due to the various processes examined at VUT, this
work picks up the opportunity to compare the different tar amounts and compositions at different
temperatures and process parameters. The tar content and composition in the producer gas of steam
gasification of straw and wood as well as the tar yields of low temperature pyrolysis of straw are
displayed in the following work. Gasification experiments were carried out in a 100 kW dual fluidized bed steam gasifier at a temperature range of 700° C to 870° C. Pyrolysis experiments were conducted in a rotary kiln
reactor at temperatures between 600° C and 630° C. For better understanding of tar formation during thermo-chemical conversion of biomass the tar content and composition in the producer gas was analyzed with a gas chromatograph coupled with a mass spectrometer. Main observation was that at higher temperatures the tar composition is shifted to higher molecular tars as poly aromatic hydrocarbons (PAH). Key tar components at lower temperatures (pyrolysis) are phenols. These results give the opportunity to analyse tar formation in different thermochemical conversion steps, therefore, for the future a better understanding of tar formation in large scale facility’s should be gained. This means lower tar content in the producer gas for gasification processes and an achievement of required pyrolysis oil yields for pyrolysis.

This paper focusses on the elaboration of the potential of the waste sector to contribute to the provision of 100% renewable energy systems. Waste is an abundant and locally available ressource and in many cases it is (at least partially) of biogenic origin, therefore pursuing political goals in waste management by energetic utilization of waste contributes towards achieving political goals in the energy as well as climate policy, too. However, it is shown based on the example of Austria that looking at energy systems on a national or international scale the waste sector is only able to contribute very little to the provision of the overall energy needed. It is different if one looks at specific energy systems in industrial sectors or on individual industrial sites. Here one must aknowledge that the energetic utilization of waste can have a high impact towards establishing renewable energy systems. Exemplarily this is shown by discussing the Austrian pulp & paper as well as the cement industry sector.

Heterogeneous wastes, which cannot be material-recycled easily are used for energetic utilization. Certain quality criteria need to be met in this context, addressing especially the chlorine content due to the product quality as well as to environmental and safety issues. In regard of current issues in climate policy concerning emission trading, also an increased biogenic content in these waste fractions is desirable. Therefore, experiments with a sensor-based sorting technology at pilot scale as well as large scale have been conducted to analyse the technical feasibility of this technology for its application on heterogeneous wastes to gain products with desired material and quality criteria. The results of pilot scale experiments show that the sensor-based sorting technology is generally technically feasible to gain waste fractions with the required characteristics, if the technology was adjusted to the specific waste stream. Due to restrictions during the large scale experiment a number of further issues need to be addressed in
further experiments to allow for a concluding evaluation of that treatment concept.

In Güssing a nearly nitrogen free product gas can be provided by the Fast Internal Circulating Fluidized Bed (FICFB) – gasification system. The main components of the product gas are hydrogen (H2), carbon monoxide (CO), carbon dioxide (CO2) and methane (CH4). A Fischer – Tropsch (FT-) trial plant uses the product gas components H2 and CO in an exothermic, catalytic reaction to produce hydrocarbon chains. Catalysts based on iron and cobalt are used for the synthesis. In Güssing a slurry reactor is used for low temperature FT – synthesis. The main parts of the plant are the gas cleaning section, the gas compression section, the FT – slurry reactor and the product separation section. In the year 2008 eight experiments with a catalyst based on iron and from April to July 2009 ten experiments with a catalyst based on cobalt were done. Over 1400 operating hours were reached and approximately 170 kg of FT – raw product was produced. The product of the experiments with cobalt catalyst was split into the fractions naphtha, diesel and waxes by vacuum distillation. The long chain waxes of the distillation were used in a hydro – treater to convert them to diesel.

A polygeneration process is about to be implemented at the biomass gasification plant in Oberwart, Austria. Apart from conventional heat and electricity production, product gas obtained from steam gasification of wood chips is used for production of hydrogen. A membrane separation process was chosen for this application. Meeting the requirements of robustness and simplicity are benefits of this technology, however, maximizing of purity and output of hydrogen is not given highest priority. Simulation results show the gas compositions of both permeate and retentate stream as a function of different membrane stage-cuts. Basically high hydrogen content in the permeate stream can be achieved, but only with the drawback of low stage-cuts. Moreover, the trade-off between hydrogen purity and hydrogen recovery as well as the influence of the operating pressure on the purity are illustrated.

Because of the limited resources of fossil fuels the efficient use of renewable energy is gaining importance. Renewable energy from biomass reduces CO2 emissions, which is a necessity to protect the global climate. In the dual fluidised bed steam gasifier wood chips are converted to heat, power and other products very successfully. This work presents alternative feedstocks for this process: biomass wastes, such as waste wood, bark and reed. Waste wood and bark have been gasified successfully and first results of these experiments in the pilot plant are presented in this paper. It has been assessed that reed is also an interesting feedstock suitable for the use in fluidised bed gasifiers.

Upgrading of Fischer–Tropsch (FT) biowaxes to second-generation biofuels via hydroprocessing is the final
step for increasing the fuel amount of the overall biomass conversion route: gasification of lignocellulosic biomass, FT synthesis, and hydroprocessing. The typical FT product portfolio consists of high molecular weight paraffinic waxes as the main product and FT fuels in the diesel and naphtha boiling range. OMV's objective and contribution to the project focus on achieving coprocessing of FT biowaxes with fossil feedstock using existing hydrotreating plants of crude oil refineries. Various test runs have been examined with a conventional refining catalyst under mild conditions (380–390°C, 5.8 MPa; WHSV, 0.7–1.3 h−1) in a pilot plant. Pure FT biowax is converted to gases, fuels, and an oil/waxy residue in a fixed-bed reactor with a porous catalyst layer technology. The presence of hydrogen in the reaction chamber reduces the fast deactivation of the catalyst caused by the formation of a coke layer around the catalyst particle surface and saturates cracked hydrocarbon fragments. Another approach is the creation of synthetic biodiesel components with excellent fuel properties for premium fuel
application. Basically, premium diesel fuel differs from standard diesel quality by cetane number and cold flow
properties. Hydroprocessed synthetic biodiesel (HPFT diesel) has compared to conventional diesel advantages in many aspects. Depending on the catalyst selected, premium diesel quality can be obtained by shifting cold flow
operability properties of HPFT fuels to a range capable even under extreme cold conditions. In addition, a highquality kerosene fraction is obtained to create bio jet fuels with an extremely deep freezing point, as low as −80°C. The isomerization degree, as well as the carbon number distribution of high paraffinic profile, and the branching degree have a major impact on the cold flow properties and cetane number. FT diesel has, compared to HPFT diesel, a slightly higher derived cetane number (DCN>83) and a cloud point of −9°C, whereas HPFT diesel reaches values as low as −60°C. Although the HPFT naphtha obtained consists of high amounts of isoparaffins, the RON/ MON values are comparable to fossil straight-run naphtha. The reason is that the branching degree of isoparaffins from the naphtha fraction is not sufficiently high enough to reach the typical octane number values of gasoline products delivered at filling stations. Assuming the goal of launching a premium biodiesel or biokerosene fuel to the market, these hydroprocessed synthetic biofuels from FT biowaxes are ideal blending components.

Due to the Austrian legal framework provided by the landfill ordinance from 1996 which has been fully implemented by January 1st 2009, waste with an organic content higher than 5% TOC (total organic carbon) must not be dumped without prior treatment in order to avoid greenhouse gas emissions from landfills. Besides thermal treatment also mechanical-biological treatment (MBT) has been enabled by the regulator as an eligible treatment approach, whereby waste to be dumped must comply with the threshold of 6,600 kJ/kg DM (dry mass) stipulated for the upper caloric value. This is a tough challenge due to the high energy content of plastic, paper, cardboard and wood components which are still contained in the low caloric output fraction of the MBT of municipal and commercial waste as those materials have a much higher upper caloric value. From the resource conservation point of view the utilization of these waste components for energetic purposes is desirable too.
The implementation of the legal framework as one measure battling climate change as well as constantly rising energy prices have caused a change from pure waste management with the intention to reduce the organic content in waste, to the point where high caloric components have become a substitute for fossil fuels in certain sectors of industries (cement industry, pulp & paper industry, steel works, etc). Using waste derived or so-called refuse derived fuel (RDF) demands high purity in order to secure environmental standards as well as product quality and therefore process related requirements have to be met. This can be achieved by 1) qualified selection of the waste streams into the treatment plants and 2) by processing technologies allowing the separation of wanted/unwanted waste components within the plant concept. In cooperation with a regional waste management company, responsible for the treatment and disposal of 82,000 t/a of municipal and commercial waste and operator of a MBT plant as well as a landfill, further processing of a specific output waste stream from the MBT plant was analysed in order to allow an optimized routing of the output streams including the energetic utilization of high caloric components and landfilling of low caloric and inert components. Experiments using the innovative treatment technology of sensor based sorting were conducted with a waste stream characterized by 59 % high caloric components (polymers, paper and cardboard, wood), 8 % other organic components, 27 % inert waste, 3 % metals and 3 % other waste (textiles, fine fraction < 20 mm, hazardous waste). The particle size of that particular waste stream is 20-80 mm. The sorting machine was a NIR (near infrared) multiplex sensor based sorting system with a wavelength of 1,400-1,900 nm in pilot scale. Results showed that by varying the parameters air pressure (bar), scanning speed (Hz), blow out time (ms) and the evaluation of spectra, about 76 % of polymers, 86 % of wood and 96 % of paper and cardboard of the input fractions could be separated from the inorganic waste stream. The remaining components were inert waste (53%), metals (3 %), other waste (textiles, contaminated waste, fine fraction < 20 mm) (3 %), but also dark polymers (12 %), undefined organics (e.g. fruits, vegetables) (9%) and still 20 % of polymers, wood, paper and cardboards. Due to the high portion of organic components and dark polymers in the stream, the threshold of 6,600 kJ/kg DM defined for waste to be landfilled could not be met. Further experiments with a more sensitive sorting system, a spectral imaging technology (wavelength up to 2,500 nm), are planned, supposing that the rejection rate of dark polymers could be increased. Theoretical considerations have shown that in that case the threshold could be met.

A new mathematical model for the grate combustion of biomass has been derived from physical considerations. Various models for grate combustion can already be found in the literature. Usually their intention is to simulate the real situation in a furnace as precisely as possible. Hence they are very detailed, typically consisting of many partial differential equations. However, because of their complexity they are useless for control purposes. The new model is very simple, consisting of only two ordinary differential equations, which makes it particularly suitable as a basis for model based control strategies. To verify the model, experiments were performed at a pilot scale furnace with horizontally moving grate. The pilot plant is a downscaled version (180 kW_th) of a typical medium scale furnace in terms of geometry and instrumentation. Comparison of the measured and calculated values shows good agreement. © 2009 Elsevier Ltd. All rights reserved.

The design and optimisation of a biomass grate furnace requires accurate and efficient models for the
combustion process on the grate as well as the turbulent reactive flow in the combustion chamber. Computational Fluid Dynamics (CFD) have been successfully applied for gas phase combustion. However, no numerical models for the biomass packed bed combustion, which can be used as engineering design tools, are commercially available at present. This paper presents an innovative 3D CFD model for biomass packed bed combustion consisting of an Euler-Granular model for hydrodynamics of gas-particle multiphase flow and a thermally thin particle model for combustion of biomass particles. Modelling the particle trajectories and the thermal conversion of each particle in the bed constitutes the simulation of the entire bed combustion. The simulation of a small-scale underfeed stoker furnace of KWB has been successfully performed by the application of the new packed bed combustion model. The positions of the drying, pyrolysis and char burnout zones in the fuel bed as well as the temperature distribution among the particles seem to be plausible and could be confirmed by observations. Furthermore, a good qualitative agreement concerning the flue gas temperatures measured by thermocouples at different positions in the combustion chamber, and CO emissions measured at boiler outlet could be achieved. The new packed bed model provides the advantages of considering the release profiles of species and energy from the fuel bed close to reality and enables to consider the chemical compositions, size and physical properties of the fuel particles as well as the influence of primary air
distribution and grate motion on the particle trajectories.

In cooperation between Vienna University of Technology and Bioenergy 2020+ a project was done which had the objective to evaluate the prospects for the production of Biofuels by integration in existing Austrian biomass industry. The advantages of such integration are the good access to renewable energy resources like wood chips, existing infrastructure for electricity and heat, existing logistics of resources and the utilization of waste heat from Biofuel production to substitute fossil fuels. One work package included the process simulation of thermo-chemical biomass gasification and the production of a second generation Biofuel by the use of Fischer – Tropsch (FT) - synthesis. The process simulation tool IPSEpro was used for the simulation. The simulation of technical processes allows the prediction of the behavior of processes on the base of mathematical models. The quality of a simulation model depends substantially on the used model and the process parameters. The used technologies in the process simulation were the biomass gasification with the Fast Internal Circulating Fluidized Bed (FICFB) – gasification system and the Fischer –Tropsch (FT) - synthesis. The FICFB was developed by the Vienna University of technology. This gasification technology is used in the well known demonstration plant is Güssing (Austria). The produced product gas is nearly nitrogen free and has a high content of hydrogen (45 – 35 Vol%_dry) and carbon monoxide (25 – 20 Vol%_dry). These product gas components are used in the FT - synthesis for the production of FT – raw product. A FT - Trial Plant is also situated in Güssing since the year 2005. A slurry reactor is used in the Trial Plant for the FT – synthesis. The target for the simulation was the production of FT – raw product as well as the substitution of fossil fuels. The waste heat of the process should be used for the production of steam. An amount of 120 tons per hour of fossil produced steam should be substituted. The
Off-Gas of the FT – process was also used for the production of steam. Two different models for location number one were considered. The used fuel was wood chips. The data out of the simulation were used to calculate the economic efficiency of the plants. An important parameter was the price of the FT – raw product per liter. The total costs and the production capacity were set equal to calculate the marginal revenue. Also a sensitivity analysis was done to evaluate the effects of rising fuel costs and increased investment costs.

A pyrolysis process can be used to split up the biomass in a volatile fraction poor in undesired substances (Cl, N, S,
Na and K) and a char fraction where these substances are concentrated. In this way cheap biomass can be used for cofiring in existing fossil fuel power stations without the danger of corrosion, deposition, and emission problems. The aim of the project is the development and demonstration of a biomass pretreatment process based on pyrolysis in the temperature range between 450-650 °C to split the energy in the biomass into volatiles with a low content of the above mentioned undesired compounds and char, where most of these pollutants are concentrated. The balance of the system can provide important results, such as the development of the product spectrum by a function of the operating parameters. Based on the results of the pilot plant a scale up to a capacity of 30 MWth fuel input and the connection with the coal fired power plant is currently investigated.

A pyrolysis process can be used to split up the biomass in a volatile fraction poor in undesired substances (Cl, N, S,
Na and K) and a char fraction where these substances are concentrated. In this way cheap biomass can be used for cofiring in existing fossil fuel power stations without the danger of corrosion, deposition, and emission problems. The aim of the project is the development and demonstration of a biomass pretreatment process based on pyrolysis in the temperature range between 450-650 °C to split the energy in the biomass into volatiles with a low content of the above mentioned undesired compounds and char, where most of these pollutants are concentrated. The balance of the system can provide important results, such as the development of the product spectrum by a function of the operating parameters. Based on the results of the pilot plant a scale up to a capacity of 30 MWth fuel input and the connection with the coal fired power plant is currently investigated.

By using a microwave generator as energy source wood gets converted into three products: (1) condensate (“product oil”), (2) product gas and (3) charcoal (“material residue”). In this microwave-based specific kind of pyrolysis process wood is used as standard input material in order to have the possibility to compare the three generated products either with products of already established conventional pyrolysis processes [1] or other processes like gasification within thermo-chemical conversion [2]. Therefore, a discontinuous microwave apparatus of technical standard size (magnetron power: 6 kW, magnetron frequency: 2.45 GHz) is used.

While reasonably accurate in simulating gas phase combustion in biomass grate furnaces, CFD tools based on simple turbulence-chemistry interaction models and global reaction mechanisms have been shown to lack in reliability regarding the prediction of NO_x formation. Coupling detailed NO_x reaction kinetics with advanced turbulence-chemistry interaction models is a promising alternative, yet computationally inefficient for engineering purposes. In the present work, a model is proposed to overcome these difficulties. The model is based on the Realizable k-ε model for turbulence, Eddy Dissipation Concept for turbulence-chemistry interaction and the HK97 reactionmechanism. The assessment of the sub-models in terms of accuracy and computational effort was carried out on three laboratory-scale turbulent jet flames in comparison with the experimental data. Without taking NO_x formation into account, the accuracy of turbulence modelling and turbulence-chemistry interaction modelling was systematically examined on Sandia Flame D and Sandia CO/H2/N2 Flame B to support the choice of the associated models. As revealed by the Large Eddy Simulations of the former flame, the shortcomings of turbulence modelling by the Reynolds averaged Navier-Stokes (RANS) approach considerably influence the prediction of the mixing-dominated combustion process. This reduced the sensitivity of the RANS results to the variations of turbulence-chemistry interaction models and combustion kinetics. Issues related to the NO_x formation with a focus on fuel bound nitrogen sources were investigated on a NH3-doped syngas flame. The experimentally observed trend in NO_x yield from NH3 was correctly reproduced by HK97, whereas the replacement of its combustion subset by that of a detailed reaction scheme led to a more accurate agreement, but at increased computational costs. Moreover, based on results of simulations with HK97, the main features of the local course of the NO_x formation processes were identified by a detailed analysis of the interactions between the nitrogen chemistry and the underlying flow field. © 2011 Taylor & Francis.

Minimizing carbon dioxide emissions whereas keeping up the high living standard of today is only possible by increasing the efficiency of energy consumption and the change to a mix of renewable fuels. Huge amounts of unused biomass in terms of agricultural residues like straw, that is a cheap and local feedstock, are often available. But as a reason of the high amount of corrosive ash elements (K, Cl, S), the residues are not suitable for co-firing in a thermal power plant. Therefore the feedstock is converted by low temperature pyrolysis into pyrolysis gases and charcoal. The aim of this work is to obtain fundamentals for an advanced pyrolysis model approach by the results of the pilot plant for co-firing the pyrolysis gases in a thermal power plant. A 3 MW pyrolysis pilot plant is being operated since 2008. For the process, an externally heated rotary kiln reactor with a design fuel power of 3 MW is used. Several mass and energy balances have been calculated based on measured plant data for different operating points of the pilot plant. The high amount of pyrolysis oil in the gas has positive effects to the heating value of the pyrolysis gases. As a reason of that, cold gas efficiencies of more than 70 % are possible. Based on these results, a scale up to a next scale pyrolysis reactor with a capacity of 30 MWth fuel input is currently investigated.

In this paper a stochastic cellular automata model is examined, which has been developed to study a "small" world, where local changes may noticeably alter global characteristics. This is applied to a climate model, where global temperature is determined by an interplay between atmospheric carbon dioxide and carbon stored by plant life. The latter can be released by forest fires, giving rise to significant changes of global conditions within short time.

In the last decades certification tests of small-scale biomass systems have impressively shown the improvement of the state of the art. Though, steady state measurements represent results only foroptimal operation. In practice results differ due to varying operating conditions. Therefore, of a test stand measurement method to derive realistic annual system efficiencies and emission factors is developed. The method includes a heat loss model for thermal storages too. It can be used to test automatically fed biomass boiler, manually loaded biomass boilers and boiler / heat accumulator combinations. For the evaluation of the measurement data a calculation method based on mass flows was developed. The results of our experiments show that the newly developed method is a good tool to evaluate small-scale biomass boilers. With this method an easy and reliable instrument to determine annual system efficiencies and emission factors for realistic boiler operation is provided. The application of the method will prove that modern small-scale biomass combustion systems have the potential to significantly contribute to the reduction of air pollutants and to increase overall energy system efficiency.

The processing of heterogeneous waste is a major challenge for waste treatment equipment used in mechanical-biological (MB) waste treatment plants. This conference contribution focuses on the technical feasibility and efficiency of different technologies for the processing of a heavy waste fraction from a MB-plant which contains a high portion of high caloric components. The aim is to meet the requirements for waste to be landfilled in Austria. Also economic considerations with regard to the implementation of an additional separation step and the resulting changes in the waste routing are discussed. The processing technologies looked at comprise sensor-based sorting technologies (NIR, X-ray transmission) as well as traditional mechanical density separation technologies such as a jigger and cross-flow air classification.

A one-dimensional model for the thermal conversion of thermally thick biomass particles is developed for the simulation of the fuel bed of biomass grate furnaces. The model can be applied for cylindrical and spherical particles. The particle is divided into four layers corresponding to the main stages of biomass thermal conversion. The energy and mass conservation equations are solved for each layer. The reactions are assigned to the boundaries. The model can predict the intra-particle temperature gradient, the particle mass loss rate as well as the time-dependent variations of particle size and density, as the most essential features of particle thermal conversion. When simulating the fuel bed of a biomass grate furnace, the particle model has to be numerically efficient. By reducing the number of variables and considering the lowest possible number of grid points inside the particle, a reasonable calculation time of less than 1 min for each particle is achieved. Comparisons between the results predicted by the model and by the measurements have been performed for different particle sizes, shapes and moisture contents during the pyrolysis and combustion in a single-particle reactor. The results of the model are in good agreement with experimental data which implies that the simplifications do not impair the model accuracy.

This thesis focuses on portraying the thermal behavior of a biomass pellet boiler through measurement and simulation. During operation the power of a pellet boiler changes depending on the heat demand. Detailed measurements were conducted to record this changing behavior of some boilers and estimate their levels of efficiencies. Subsequently a mathematical model was created to emulate boilers and their thermal performance without such measurements. The first part of this thesis deals with the description of the simulation model and the measurements which were carried out. Secondly, the verification of the model is discussed. For this verification simulation results of three different boilers are compared to measurement data and pictured in various diagrams. The last part of this thesis is about further simulations of these three boilers where the control units were emulated too. The model was built in the MATLAB/Simulink® environment and is generally based on
thermodynamic relationships and heat balances in a boiler. However, through constant comparison of the simulation results with the measurement data some parameters were adapted to fit the simulation to reality. Therefore this model is “semi-empirical” as physical correlations are included but some parameters were deduced from measurement. Following, the verification of the model is discussed through the comparison of measurement data and simulation results. For the verifications the boiler power, fuel mass flow as well as
the heat consumption were taken from the measurement data and set as input for the simulation. The calculated results show that the boiler model enables to portray the thermal behavior of the three boilers tested with only small divergences. At the end of this thesis it was attempted to model the control unit of the three boilers by analyzing the measurement data. Having a model for the control unit, the inputs from the measurement data are reduced to just two variables, the water inlet temperature and the water volume flow (heat consumption). The comparison of the calculated values to the measurement data shows slightly higher divergences than during the validation, especially where the simulated control unit does not behave like the real one. Through the simulation of further boilers the model could be continuously enhanced. In the future this “virtual boiler” should be used to test control algorithms of boiler control units to enhance their efficiencies.

To examine relevant combustion characteristics of biomass fuels in grate combustion systems, a specially designed lab-scale reactor was developed. On the basis of tests performed with this reactor, information regarding the biomass decomposition behavior, the release of NO_x precursor species, the release of ash-forming elements, and first indications concerning ash melting can be evaluated. Within the scope of several projects, the lab-scale reactor system as well as the subsequent evaluation routines have been optimized and tests with a considerable number of different biomass fuels have been performed. These tests comprised a wide variation of different fuels, including conventional wood fuels (beech, spruce, and softwood pellets), bark, wood from short rotation coppice (SRC) (poplar and willow), waste wood, torrefied softwood, agricultural biomass (straw, Miscanthus, maize cobs, and grass pellets), and peat and sewage sludge. The results from the lab-scale reactor tests show that the thermal decomposition behavior and the combustion behavior of different biomass fuels vary considerably. With regard to NO_x precursors (NH₃, HCN, NO, N₂O, and NO₂), NH₃ and, for chemically untreated wood fuels, also HCN represent the dominant nitrogen species. The conversion rate from N in the fuel to N in NO_x precursors varies between 20 and 95% depending upon the fuel and generally decreases with an increasing N content of the fuel. These results gained from the lab-scale reactor tests can be used to derive NO_x precursor release models for subsequent computational fluid dynamics (CFD) NOx post-processing. The release of ash-forming vapors also considerably depends upon the fuel used. In general, more than 91% of Cl, more than 71% of S, 1–51% of K, and 1–50% of Na are released to the gas phase. From these data, the potential for aerosol emissions can be estimated, which varies between 18 mg/Nm³ (softwood pellets) and 320 mg/Nm³ (straw) (dry flue gas at 13% O2). Moreover, these results also provide first indications regarding the deposit formation risks associated with a certain biomass fuel. In addition, a good correlation between visually determined ash sintering tendencies and the sintering temperatures of the different fuels (according to ÖNORM CEN/TS 15370-1) could be observed.

Der Einfluss von Nährstoffzusammensetzung und Additivzugabe beim anaeroben Abbau organischer Substanz stieß in den letzten Jahren vermehrt auf Interesse. Im Besonderen Spurenelemente haben erwiesenermaßen erheblichen Einfluss auf u.a. methanogene Archaeen und deren metabolische Aktivität. Massive Probleme der Prozessstabilität speziell bei Monovergärung unterschiedlichster Substrate können durch Co-Fermentation oder gezielte Zudosierung von Spurenelementmischungen überwunden werden. Ein profundes Verständnis der Wirkung dieser Elemente auf die verschiedenen mikrobiellen Spezies im Biogasreaktor als auch ihre Verfügbarkeit, ist die Voraussetzung für eine wirtschaftliche Gestaltung des anaeroben Fermentationsprozesses organischer Roh- als auch Reststoffe. Der heutige Stand-der-Technik zur Analyse von Biogasproben hat seinen Ursprung in der Wasser-, Abwasser- und Schlammanalytik und besteht aus einem einzelnen Filtrationsschritt vor Elementdetektion mittels ICP-OES bzw. ICP-MS. Diese Methodik erlaubt nur einen äußerst begrenzten Einblick in die Verteilung von essentiellen Spurenelementen in Anaerobreaktoren. Eine aussagekräftige Beurteilung der mikrobiellen Verfügbarkeit von beispielsweise Cobalt, Nickel oder Molybdän ist somit nur eingeschränkt möglich. Ziel dieser Arbeit war es, eine bestehende Methode zur sequentiellen Extraktion aus dem Bereich der Boden- und Sedimentanalytik für die Anwendung auf Biogasproben zu adaptieren. Der daraus resultierende Einblick in die Verteilung von Spurenelementen in den einzelnen Fraktionen erlaubt eine genauere Bewertung der mikrobiellen Verfügbarkeit von Nährstoffen in Biogasreaktoren, verglichen mit bestehenden analytischen Untersuchungsmethoden. Anforderungen an das Verfahren wie die Reproduzierbarkeit der Daten, zeitsparende Analytik und wirtschaftliche Realisierbarkeit konnten erfüllt werden. Wiederfindungsraten zwischen 90 und 110 % wurden für die wichtigsten Spurenelemente erreicht. Durch die sequentielle Extraktion konnte gezeigt werden, dass essenzielle Mikro-Nährstoffe bis zu 98 % in einer unlöslichen Form vorliegen können. Die Ergebnisse dieser Arbeit belegen die Anwendbarkeit der entwickelten Methodik zur Spurenelement-Extraktion in Anaerob-Systemen.